It’s certainly true that there is no central authority in Judaism at this particular point in history. But it is equally true that such an authority did exist in the past – Moses himself was such an authority, and his successors continued it for many generations.
On the one hand we have free will to interpret the Torah however we want. But on the other hand, not all interpretations are equally valid. It seems prudent to see what the classics say about new ideas that we might come up with.
For example, the word “work” is not the only source for deciding what to forbid on the Sabbath. Consider, please, the beginning of Chapter 35 of the book of Exodus. Keep in mind that from here to the end of that book is devoted exclusively to the instructions of how to build the Tabernacle – the mini-Temple – of the Israelites in the desert.
The rabbis of the Talmud ask (rhetorically) why this concept is used to introduce the directions for building the Tabernacle. Their answer is that we must continue our work on the Tabernacle for all six days of the week, but to stop all that work on the Sabbath. In other words, if an act must be done for the building of the Tabernacle, then it is an act which must not be done on the Sabbath.
The rabbis’ next step was to catalog and categorize all those activities, so that we’ll know which ones to avoid. And because the wood of the beams needed to be cut to specific sizes and shapes, and the leather of the wall coverings had to be cut to specific sizes and shapes, one of those categories became known as “cutting to a specific size or shape”. which is why I don’t tear my toilet paper on the Sabbath.
(And, as my aunt remarked when I explained this to her: “And because they needed curtains, that’s why I can’t do my sewing!”)